1. Field of the Invention
The apparatus of the present invention relates to prosthetic feet and ankles. More particularly, the present invention relates to an artificial prosthetic device which provides multi-axial rotation for an artificial ankle mounted on an artificial foot.
2. General Background
In area of prosthetic limbs, artificial feet and ankles normally been constructed as a solid ankle cushion heel foot known as a S.A.C.H. foot attached or mounted to a limb along an approximate hinge axis taken through the ankle. It is critical that the foot and the ankle in artificial limbs operate as a single unit, in order to result in the proper bio-mechanics of the entire lower limb in assisting the wearer in walking and of the movement. The conventional S.A.C.H. foot has been the most widely prescribed artificial foot over the past thirty (30) years. The S.A.C.H. foot provides a stable base for a prosthesis, and addresses the concept of absorbing and storing energy as the heel of the foot strikes the surface and gradually releasing the energy through the remainder of the gate cycle. The newer S.A.C.H. foot has become known as a "energy storing foot". As new lightweight composite materials become available, energy storing feet become a practical alternative to the convention S.A.C.H. feet. Propulsion is provided by using a leaf spring mechanism inside a plastic shell of the artificial foot that stores and releases energy. This assists the amputee during the gait cycle by providing lift and thrust for the prosthesis.
Applicant has obtained U.S. Pat. No. 4,718,913 entitled "Dual, Ankle, Springs Prosthetic Foot and Ankle System", which provides a dual ankle spring foot/ankle system having a first and second helical springs attached to a top ankle plate and distally to a plantar base plate. The anterior and posterior springs are attachably engaged to the plates through a helical nut for helically engaging the spring around its body portion and attaching the spring to the plates themselves. The helical attachment loses no flexion as would occur with welding or the like. Further it provides the necessary propulsion and movement of the ankle in combination with artificial feet, such as the S.A.C.H. foot.